People get the idea that they need to bury their gardens under truckloads of compost to get good results; however, in most areas of the country, less than a half-inch-thick layer each year is plenty.
Nitrogen is the main nutrient you need to provide your plants. Most edible crops need an annual application of only about 11/44 pound of nitrogen per 100 square feet, and lawns and ornamentals need even less than that. In most regions, a yearly rate of just 1/2 inch of compost containing 1 percent nitrogen (about four 40-pound bags or 30 gallons per 100 square feet) will accumulate enough organic matter in the soil to provide ample nutrients for excellent plant growth. In the longer growing seasons of the South and in areas with very high rainfall, that annual rate should be doubled to 1 inch. For one-time applications to new garden beds, you can double or even triple the annual rate if you’re sure you have a good-quality compost.
Reprinted with permission from Organic Gardening Magazine